Modulation of smooth muscle cell proliferation

ABSTRACT

There is provided a novel use for vascular endothelial growth factor, herein designated VEGF-X, and a CUB domain present in the sequence of VEGF-X, which enhance smooth muscle cell proliferation and can be used to treat diseases associated with reduced smooth muscle cell proliferation. VEGF-X, and a CUB domain can also be used in tissue engineering applications to increase the number of smooth muscle cells within specific tissue to restore that tissue function or architecture. Screening methods for identifying inhibitors of VEGF-X biological activity are also disclosed and these inhibitors include neutralizing VEGF-X antibodies, antisense VEGF-X sequences or non-protein antagonists competing with VEGF-X biological activity. Also provided are therapeutic methods for treating disorders associated with smooth muscle cells hyperproliferation and methods of diagnosis a pathological condition or susceptibility to a pathological condition associated with smooth muscle cell hyperproliferation.

This application claims the benefit of U.S. provisional application Ser. No. 60/274,901, filed Mar. 9, 2001, and is the national stage application filed on Sep. 5, 2003 of the International Application No. PCT/EP02/02616 which has an international filing date of Mar. 7, 2001, each of which is incorporated herein by reference.

The present invention is concerned with modulation of smooth muscle cell proliferation and, in particular, with a novel use of vascular endothelial growth factor to enhance smooth muscle cell proliferation and to treat diseases associated with reduced smooth muscle cell proliferation.

The PDGF/VEGF growth factor family contains a number of structurally related growth factors. Members of the family contain a conserved cysteine-rich region, the cysteine knot (Sun, P. D. 1995), which forms dimers covalently linked by inter-chain disulphide bonds (Potgens et al. 1994, Andersson et al. 1992). Platelet-derived growth factor (PDGF) is mitogenic for connective tissue cells, including fibroblasts and smooth muscle cells (reviewed in Heldin et al. 1999). PDGF consists of homo- and heterodimers of distinct A and B chains, and activates two receptor tyrosine kinases, PDGFR-α and PDGFR-β. PDGF mRNA is expressed in a range of normal cell types and may be involved in tumorigenesis and other disease processes (Heldin et al. 1999). Furthermore, the PDGF-B gene is carried by transforming retroviruses as the v-sis oncogene (Devare et al., 1983), indicating that overexpression can be oncogenic.

The vascular endothelial cell growth factors are involved in neovascularisation and vascular permeability (reviewed in Ferrara & Davis-Smyth, 1997, Neufeld et al., 1999). To date five endogenous VEGFs (VEGF-A, -B, -C, -D and placenta growth factor (PLGF)) have been described. VEGF signaling is via a family of receptor tyrosine kinases (Ferrara & Davis-Smyth, 1997, Neufeld et al., 1999), though it has recently been shown that neuropilin-1 is also a receptor for some isoforms of VEGF-A (Soker et al., 1998).

VEGF-A is expressed in several normal tissues including heart, placenta and pancreas (Berse et al., 1992). It has been shown to be over-expressed in many tumors (Takahashi et al., 1995), and inhibition of VEGF-A action has been shown to cause tumor regression in animal models (Kim et al., 1993). VEGF-A has been also implicated in other disease processes involving inappropriate angiogenesis (Folkman 1995). VEGF-B mRNA expression in normal tissues overlaps with that of VEGF-A, but is also detectable in the central nervous system (Lagercrantz et al, 1998). VEGF-C is expressed at lower levels than VEGFs A and B (Lagercrantz et al, 1998), but is detectable in a range of tissues (Lee et al. 1996, Fitz et al., 1997). VEGF-D is strongly expressed in lung, heart and small intestine, and is detectable in several other tissues (Yamada et al, 1997).

A search of EST databases resulted in the identification of a new member of the VEGF/PDGF family. The identified polypeptide sequence contains an N-terminal CUB domain and a C-terminal PDGF domain, and which has been designated VASCULAR ENDOTHELIAL GROWTH FACTOR-X (VEGF-X; Patent WO 0037641; EMBL accession number AX028032). The same sequence has recently been published and shown to have PDGF activity (Li et al., 2000) and named PDGF-C and these two designations may be interchangeably used. Li et al found that the C-terminal PDGF domain of PDGF-C was active in PDGFR binding and stimulation of fibroblast proliferation, whereas the full-length PDGF-C showed no such activity. They proposed a model in which the CUB domain functions as an inhibitor of the PDGF domain: activation is via proteolysis to release the active PDGF-C.

Smooth muscle cells are important in the urethra and bladder wall to control bladder function. Increasing the number of smooth muscle cells has been demonstrated to be a therapy for stress urinary incontinence and bladder dysfunction (Yokoyama et al., 2000). The increase in cell number used as a therapy has been to directly inject smooth muscle cells (myoblasts) into the urethra and bladder wall.

On the other hand, arterial smooth muscle cell hyperplasia is known to cause various diseases and the agents that block this undesirable cellular level event could be used in drug targeted therapy for these diseases. Atherosclerosis, a disease of the large arteries, is the primary cause of heart disease and stroke. In westernized societies, it is the underlying cause of about 50% of all deaths. Atherosclerosis is a progressive disease characterized by the accumulation of lipids and fibrous elements in large arteries. The overgrowth of cells of the vessel wall, especially of the smooth muscle cells (SMCs), contributes to the pathogenesis of atherosclerosis (Lusis, A J, 2000). A treatment that could block the smooth muscle cell proliferation and migration would be sufficient to prevent intimal hyperplasia and might also contribute to the vascular healing process. In the current vascular interventional environment, high restenosis rates have increased awareness of the significance of intimal hyperplasia, a chronic structural lesion that develops after vessel wall injury, and which can lead to luminal stenosis and vessel occlusion. Intimal hyperplasia is defined as the abnormal migration and proliferation of vascular smooth muscle cells with associated deposition of extracellular connective tissue matrix (Hagen P. O., et al. 1994). Cardiac allograft arteriosclerosis is one of the major reasons for limiting long-term survival of recipients. It is characterized by intimal thickening comprised of proliferative smooth muscle cells, which may occur at the site of anastomosis because of extensive damage to the arterial wall (Suzuki J, et al. 2000). Prevention of pathological hyperproliferation of smooth muscle cells could be used to reduce the intimal hyperplasia of healing microarterial anastomoses and allograft arterial intimal hyperplasia (Robert C, et al. 1995). Arresting the growth of smooth muscle cell pericytes will help to reduce the neointimal hyperplasia induced by coronary angioplasty. Urinary bladder or kidney hypertrophy and hyperplasia are well recognized in diabetic cystopathy. The hyperproliferation of smooth muscle cells also could cause the irreversible alterations in bladder and kidney function that result from chronic and/or severe bladder outlet obstruction (Mumtaz F H, et al 2000).

It has now been surprisingly found that both the recombinant full-length VEGF-X and the CUB domain proteins exhibit a mitogenic activity on human artery smooth muscle cells in vitro, suggesting a function for the CUB domain beyond its role in maintaining latency of the PDGF domain. Therefore VEGF-X and a CUB domain which increases smooth muscle cell proliferation may be advantageous in the therapy of urinary incontinence, bladder dysfunction and dysfunction of other sphincter composed of smooth muscle cells. VEGF-X and a CUB domain can also be used during reconstruction of the pelvic floor to improve smooth muscle function.

Therefore, according to a first aspect of the present invention there is provided use of a nucleic acid molecule encoding a VEGF-X polypeptide or functional equivalents, derivatives or variants thereof in the manufacture of a medicament to stimulate smooth muscle cell proliferation in vivo or in vitro. Preferably, the sequence of the VEGF-X polypeptide is as depicted in FIG. 1( a). Also provided is the use of the CUB domain of VEGF-X, which preferably consists of the amino acid sequence from position 40 to 150 depicted in FIG. 1( a) or a functional equivalent, derivative or variant thereof, to stimulate smooth muscle proliferation in vivo or in vitro. The aforementioned polypeptides, CUB domain and nucleic acid molecules may also be used as a medicament or in the preparation of a medicament for treating urethral dysfunction, bladder dysfunction, sphincter dysfunction or other diseases or conditions associated with reduced expression of functional VEGF-X or CUB domain proteins or for pelvic floor reconstruction. In a further aspect of the invention there is provided the use of VEGF-X or the CUB domain thereof for populating matrices with smooth muscle cells for in vivo or in vitro tissue engineering applications.

The DNA molecules according to the invention may, advantageously, be included in a suitable expression vector to express VEGF-X encoded therefrom in a suitable host. Incorporation of cloned DNA into a suitable expression vector for subsequent transformation of said cell and subsequent selection of the transformed cells is well known to those skilled in the art as provided in Sambrook et al. (1989), Molecular Cloning, a Laboratory Manual, Cold Spring Harbour Laboratory Press.

An expression vector according to the invention includes a vector having a nucleic acid according to the invention operably linked to regulatory sequences, such as promoter regions, that are capable of effecting expression of said DNA fragments. The term “operably linked” refers to a juxtaposition wherein the components described are in a relationship permitting them to function in their intended manner. Such vectors may be transformed into a suitable host cell to provide for expression of a polypeptide according to the invention.

Such expression vectors may also be used to stimulate smooth muscle cell proliferation and also in the treatment of the diseases or conditions according to the invention including urethral dysfunction, bladder dysfunction or other diseases associated with reduced expression of functional VEGF-X protein.

The polypeptide according to the invention may be recombinant, synthetic or naturally occurring, but is preferably recombinant. Similarly, the nucleic acid sequences, according to the invention may be produced using recombinant or synthetic techniques, such as, for example, using PCR cloning mechanisms.

According to a further aspect, the present invention provides for the use of pharmaceutical compositions comprising a therapeutically effective amount of a polypeptide according to the invention, such as the soluble form of a polypeptide, or nucleic acid molecule of the present invention, or a vector incorporating said nucleic acid molecule in combination with a pharmaceutically acceptable carrier or excipient. Such carriers include, but are not limited to, saline, buffered saline, dextrose, water, glycerol, ethanol, and combinations thereof. The pharmaceutical composition according to this aspect of the invention may be used to stimulate smooth muscle cell proliferation in tissue and organs, or alternatively, to treat or prevent any of urethral, bladder or sphincter dysfunction or a dysfunction associated with aberrant endogenous activity of a VEGF-X polypeptide of the invention.

The invention further relates to pharmaceutical packs and kits comprising one or more containers filled with one or more of the ingredients of the aforementioned compositions of the invention. Polypeptides and other compounds of the present invention may be employed alone or in conjunction with other compounds, such as therapeutic compounds.

The protein or polypeptide (which term is used interchangeably herein) according to the invention is defined herein as including all possible amino acid variants encoded by the nucleic acid molecule according to the invention including a polypeptide encoded by said molecule and having conservative amino acid changes. Conservative amino acid substitution refers to a replacement of one or more amino acids in a protein which do not affect the function or expression of the protein. Proteins or polypeptides according to the invention are further defined herein to include variants of such sequences, including naturally occurring allelic variants which are substantially homologous to said proteins or polypeptides. In this context, substantial homology is regarded as a sequence which has at least 70%, preferably 80 or 90% and preferably 95% amino acid homology with the proteins or polypeptides encoded by the nucleic acid molecules according to the invention. “Functional equivalent” of a protein or polypeptide in accordance with the invention encompasses all the amino acid and allelic variants envisaged above exhibiting VEGF-X activity as required by the methods and uses of the invention. The protein or polypeptide according to the invention may be recombinant, synthetic or naturally occurring, but is preferably recombinant.

A protein or polypeptide in accordance with the invention as defined herein also includes bioprecursors of said protein or polypeptides. Bioprecursors are molecules which are capable of being converted in a biological process into a protein or polypeptide having the VEGF-X activity as required by the invention. The nucleic acid or protein according to the invention may be used as a medicament or in the preparation of a medicament for treating cancer or other diseases or conditions associated with expression of VEGF-X protein.

Advantageously, the nucleic acid molecule or the protein according to the invention may be provided in a pharmaceutical composition together with a pharmacologically acceptable carrier, diluent or excipient therefor.

The present invention is further directed to inhibiting VEGF-X in vivo by the use of antisense technology.

Antisense technology can be used to control gene expression through triple-helix formation of antisense DNA or RNA, both of which methods are based on binding of a polynucleotide to DNA or RNA. For example, the 5′ coding portion or the mature DNA sequence, which encodes for the protein of the present invention, is used to design an antisense RNA oligonucleotide of from 10 to 50 base pairs in length. A DNA oligonucleotide is designed to be complementary to a region of the gene involved in transcription (triple-helix—see Lee et al. Nucl. Acids Res., 6:3073 (1979); Cooney et al., Science, 241:456 (1988); and Dervan et al., Science, 251: 1360 (1991), thereby preventing transcription and the production of VEGF-X.

Therefore, there is also provided by the present invention a method of treating or preventing any of atherosclerosis, neointimal hyperplasia caused by artery anastomosis or balloon catheter, postangioplasty restenosis caused by arterial stenting after percutaneous transluminal coronary angioplasty, said method comprising administering to said subject an amount of a polynucleotide molecule antisense to a nucleic acid molecule encoding VEGF-X polypeptide such as an antisense polynucleotide molecule capable of hybridizing to the nucleic acid according to FIG. 1( a) or the complement thereof under conditions of high stringency, in sufficient concentration to treat or prevent said disorders.

Conditions of high stringency generally include temperatures in excess of 30° C., typically in excess of 37° C., and preferably in excess of 45° C. Stringent salt conditions will ordinarily be less than 1000 mM, typically less than 500 mM and preferably less than 200 mM.

The composition may be adapted according to the route of administration, for instance by a systemic or an oral route. Preferred forms of systemic administration include injection, typically by intravenous injection. Other injection routes, such as subcutaneous, intramuscular, or intraperitoneal, can be used.

Alternative means for systemic administration include transmucosal and transdermal administration using penetrants such as bile salts or fusidic acids or other detergents. In addition, if a polypeptide or other compound of the present invention can be formulated in an enteric or an encapsulated formulation, oral administration may also be possible. Administration of these compounds may also be topical and/or localized, in the form of salves, pastes, gels, and the like.

The dosage range required depends on the choice of peptide or other compounds of the present invention, the route of administration, the nature of the formulation, the nature of the subject's condition, and the judgment of the attending practitioner. Suitable dosages, however, are in the range of 0.1-100 mg/kg of subject. Wide variations in the needed dosage, however, are to be expected in view of the variety of compounds available and the differing efficiencies of various routes of administration.

For example, oral administration would be expected to require higher dosages than administration by intravenous injection. Variations in these dosage levels can be adjusted using standard empirical routines for optimization, as is well understood in the art.

The term “therapeutically effective amount”, as used herein, means the amount of the VEGF-X, or other actives of the present invention, that will elicit the desired therapeutic effect or response or provide the desired benefit when administered in accordance with the desired treatment regimen.

A preferred therapeutically effective amount is an amount which stimulates proliferation of smooth muscle cells.

“Pharmaceutically acceptable” as used herein, means generally suitable for administration to a mammal, including humans, from a toxicity or safety standpoint.

In the present invention, the VEGF-X protein is typically administered for a sufficient period of time until the desired therapeutic effect is achieved. The term “until the desired therapeutic effect is achieved”, as used herein, means that the therapeutic agent or agents are continuously administered, according to the dosing schedule chosen, up to the time that the clinical or medical effect sought for the disease or condition being mediated is observed by the clinician or researcher. For methods of treatment of the present invention, the compounds are continuously administered until the desired change in bone mass or structure is observed. In such instances, achieving an increase of smooth muscle cells is the desired objective. For methods of reducing the risk of a disease state or condition, the compounds are continuously administered for as long as necessary to prevent the undesired condition.

The combination of two or more stimulants of smooth muscle cell proliferation are also deemed as within the scope of the present invention.

“Polynucleotide” generally refers to any polyribonucleotide or polydeoxynucleotide, which may be unmodified RNA or DNA or modified RNA or DNA. “Polynucleotides” include, without limitation, single- and double-stranded DNA, DNA that is a mixture of single- and double-stranded regions, single- and double-stranded RNA, and RNA that is mixture of single- and double-stranded regions, hybrid molecules comprising DNA and RNA that may be single-stranded or, more typically, double-stranded or a mixture of single- and double-stranded regions. In addition, “polynucleotide” refers to triple-stranded regions comprising RNA or DNA or both RNA and DNA.

The term “polynucleotide” also includes DNAs or RNAs containing one or more modified bases and DNAs or RNAs with backbones modified for stability or for other reasons. “Modified” bases include, for example, tritylated bases and unusual bases such as inosine. A variety of modifications may be made to DNA and RNA; thus, “polynucleotide” embraces chemically, enzymatically or metabolically modified forms of polynucleotides as typically found in nature, as well as the chemical forms of DNA and RNA characteristic of viruses and cells. “Polynucleotide” also embraces relatively short polynucleotides, often referred to as oligonucleotides.

“Polypeptide” refers to any peptide or protein comprising two or more amino acids joined to each other by peptide bonds or modified peptide bonds, i.e., peptide isosteres. “Polypeptide” refers to both short chains, commonly referred to as peptides, oligopeptides or oligomers, and to longer chains, generally referred to as proteins. Polypeptides may contain amino acids other than the 20 gene-encoded amino acids.

“Polypeptides” include amino acid sequences modified either by natural processes, such as post-translational processing, or by chemical modification techniques which are well known in the art. Such modifications are well described in basic texts and in more detailed monographs, as well as in a voluminous research literature. Modifications may occur anywhere in a polypeptide, including the peptide backbone, the amino acid side-chains and the amino or carboxyl termini. It will be appreciated that the same type of modification may be present to the same or varying degrees at several sites in a given polypeptide. Also, a given polypeptide may contain many types of modifications. Polypeptides may be branched as a result of ubiquitination, and they may be cyclic, with or without branching. Cyclic, branched and branched cyclic polypeptides may result from post-translation natural processes or may be made by synthetic methods. Modifications include acetylation, acylation, ADP-ribosylation, amidation, covalent attachment of flavin, covalent attachment of a heme moiety, covalent attachment of a nucleotide or nucleotide derivative, covalent attachment of a lipid or lipid derivative, covalent attachment of phosphotidylinositol, cross-linking, cyclization, disulfide bond formation, demethylation, formation of covalent cross-links, formation of cysteine, formation of pyroglutamate, formylation, gamma-carboxylation, glycosylation, GPI anchor formation, hydroxylation, iodination, methylation, myristoylation, oxidation, proteolytic processing, phosphorylation, prenylation, racemization, selenoylation, sulfation, transfer-RNA mediated addition of amino acids to proteins such as arginylation, and ubiquitination (see, for instance, PROTEINS—STRUCTURE AND MOLECULAR PROPERTIES, 2nd Ed., T. E. Creighton, W. H. Freeman and Company, New York, 1993; Wold, F., Post-translational Protein Modifications: Perspectives and Prospects, pages. 1-12 in POSTTRANSLATIONAL COVALENT MODIFICATION OF PROTEINS, B. C. Johnson, Ed., Academic Press, New York, 1983; Selfter et al., “Analysis for protein modifications and nonprotein cofactors”, Meth Enzymol (1990) 182:626-646 and Rattan et al., “Protein Synthesis: Post-translational Modifications and Aging”, Ann NYAcad Sci (1992) 663:48-62).

Polypeptides comprising any of the above modifications may be described as “derivatives” of the proteins or polypeptides in accordance with the invention.

The present invention further relates to screening methods for identifying inhibitors of VEGF-X biological activity. These inhibitors include neutralizing VEGF-X antibodies, antisense VEGF-X sequences or non-protein antagonists competing with VEGF-X biological activity. Suitable antibodies can be raised against an appropriate immunogen, such as isolated and/or recombinant antigen or its portion (including synthetic molecules, such as synthetic peptides) or against a host cell which expresses recombinant antigen. In addition, cells expressing recombinant antigen, such as transfected cells, can be used as immunogens or in a screen for antibody which binds receptor (see e.g., Chuntharapai et al., J Immunol., 152.-17831-1789 (1994).

The antibody producing cell, preferably those of the spleen or lymph nodes, can be obtained from animals immunized with the antigen of interest. The fused cells (hybridomas) can be isolated using selective culture conditions, and cloned by limiting dilution. Cells that produce antibodies with the desired specificity can be selected by a suitable assay (e.g., ELISA).

Therefore, there is also provided by the present invention a method of treating or preventing any of atherosclerosis, neointimal hyperplasia caused by artery anastomosis or balloon catheter, postangioplasty restenosis caused by arterial stenting after percutaneous transluminal coronary angioplasty, said method comprising administering to said subject an amount of an antibody capable of binding to a VEGF-X polypeptide, such as in FIG. 1( a) or an epitope thereof in sufficient concentration to treat or prevent said disorders.

Anti-VEGF-X antibodies suitable for use in the present invention are characterized by high affinity binding to VEGF-X receptor. Antibodies against VEGF-X could be administered by inhalation (e.g., in an inhalant or spray or as a nebulized mist). Other routes of administration include intranasal, oral, intravenous including infusion and/or bolus injection, intradermal, transdermal (e.g., in slow release polymers), intramuscular, intraperitoneal, subcutaneous, topical, epidural, buccal, etc. routes. Other suitable routes of administration can also be used, for example, to achieve absorption through epithelial or mucocutaneous linings. Antibodies can also be administered by gene therapy, wherein a DNA molecule encoding a particular therapeutic protein or peptide is administered to the patient, e.g., via a vector, which causes the particular protein or peptide to be expressed and secreted at therapeutic levels in vivo. In addition, anti-VEGF-X antibodies can be administered together with other components of biologically active agents, such as pharmaceutically acceptable surfactants (e.g., glycerides), excipients (e.g., lactose), carriers, diluents and vehicles. Anti-VEGFX antibodies can be administered prophylactically or therapeutically to an individual prior to, simultaneously with or sequentially with other therapeutic regimens or agents (e.g., multiple drug regimens). Anti-VEGF-X antibodies that are administered simultaneously with other therapeutic agents can be administered in the same or different compositions. Anti-VEGF-X antibodies can be formulated as a solution, suspension, emulsion or lyophilized powder in association with a pharmaceutically acceptable parenteral vehicle.

The therapeutically effective amount of VEGF-X antibody can be administered in single or divided doses (e.g., a series of doses separated by intervals of days, weeks or months), or in a sustained release form, depending upon factors such as nature and extent of symptoms, and of concurrent treatment and the effect desired.

In another aspect, a screening assay for agonists and antagonists is provided which involves determining the effect of a candidate compound on the binding of VEGF-X or CUB domain polypeptide according to the invention to a VEGF-X receptor. In particular, the method involves contacting the VEGF-X receptor with a VEGF-X or a CUB domain polypeptide according to the invention and a candidate compound and determining whether VEGF-X or CUB domain polypeptide binding to the VEGF-X receptor is increased or decreased due to the presence of the candidate compound. In this assay, an increase in binding of VEGF-X or CUB domain polypeptide over the standard binding indicates that the candidate compound is an agonist of VEGF-X or CUB domain. A decrease in VEGF-X or CUB domain polypeptide binding compared to the standard indicates that the compound is an antagonist of VEGF-X or CUB domain.

The present invention may be more clearly understood from the following example and by reference to the accompanying drawings, wherein:

FIG. 1A is an illustration of cDNA sequence of PDGF-C (SEQ ID NO: 7). The predicted PDGF-C translation product is shown above the sequence (SEQ ID NO: 1), with the predicted signal sequence underlined. The location of predicted mRNA splicing events is indicated by closed triangles. The positions of the ruRNA splicing events was inferred either from direct sequencing on an isolated BAC clone or by comparison with partial BAC sequences in the EMBL database (the region from nt. 1-374 from AC0015837, release date 7 April 2000; the region from nt. 375-571 from AC009582, release date 5 Apr. 2000). No information on splicing events is currently available for the region from nt. 900-957, indicated in italics. The cryptic splice donor/acceptor sites at nt. 719/720 and 988/989 (open triangles) were inferred from variant sequences isolated by PCR. Potential N-linked glycosylation sites in the polypeptide sequence are boxed, and FIG. 1B is a variant PDGF-C protein sequence—polypeptide sequences were predicted from PCR fragments smaller than the expected size. PCR fragments covering this region were cloned and sequenced to reveal the cryptic splice donor/acceptor sites shown in FIG. 1A. PDGF-C, var 1 and var 2 sequences disclosed as SEO ID NOS 1 and 5-6, respectively.

FIG. 2 is an illustration of the comparison of PDGF-C domains with database sequences:

(A) The PDGF domain of PDGF-C was aligned with the PDGF domains of other human PDGFs and VEGFs (SEO ID NO: 8-15, respectively, in order or appearance)

(B) The CUB domain of PDGF-C was aligned with the CUB domains of BMPs and neuropilins; proteins are from X. laevis, mouse or chicken as indicated (SEO ID NO: 16-21, respectively, in order or appearance).

All domain sequences were taken from the PFAMA database (Rocchigiani, M. et al, (1998) Genomics 47, 204-216) and aligned using the CLUSTALW alignment program (EMBL, Heidelberg, Germany). Table 1 summarizes the results of comparisons of the regions of the proteins shown in FIG. 2. From these comparisons it is clear that the degree of similarity of the CUB domain to other database sequences is higher than that of the PDGF domain.

FIG. 3 is an illustration of the results obtained from the mRNA expression of PDGF-C:

(A) Northern blot analysis of PDGF-C mRNA distribution in tissues and cancer cell lines. Control hybridisation using a β-actin cDNA probe indicated that there were equal amounts of mRNA in each lane. The position of the PDGF-C mRNA is indicated.

(B) PCR analysis on cDNA from tissues and cancer cell lines. Control using primers designed to amplify part of the glyceraldehyde-3-phosphate dehydrogenase cDNA indicated that equivalent amounts of each cDNA were present in the amplification reactions (not shown).

FIG. 4 is an illustration of the results obtained by FISH mapping of the PDGF-C (VEGF-X) locus—an example is shown: the left panel shows the FISH signals on the human chromosome, on the right is the same mitotic figure stained with 4′,6-diamidino-2-phenylindole (DAPI) to identify human chromosome 4. Also shown is a diagrammatic summary: each dot represents double FISH signals detected on chromosome 4.

FIG. 5 is an illustration of the properties of the PDGF-C recombinant proteins: (A) Glycosylation & interchain disuiphide formation. T.ni Hi5 cells were infected with baculovirus expressing full-length PDGF-C. Samples of baculovirus-infected insect cell medium were treated as follows: lane 1 - enzyme buffer+N-glycosidase F; lane 2 - enzyme buffer, no N-glycosidase F added; lane 3 -reduced; lane 4- nonreduced. Detection following Western blotting used anti His 6 (SEQ ID NO: 22) antibody to detect the introduced C-terminal epitope tag.

(B) Heparin binding. Purified E.coli-derived full-length MBP fusion protein was subjected to SDS-PAGE and the gel stained with Coomassie blue. Lane 1—loaded fraction for heparin column, lane 2 cloumn wash, lane 3—high salt elution.

(C) Full-length and CUB domain—Coomassie-stained SDS-PAGE of samples of PDGF-C full-length fusion protein (lane 1) and CUB domain (lane 2) produced in E.coli. The CUB domain was produced by refolding of insoluble material: both of the major bands at 20 and 25 kDa are detected in Western blot experiments using anti-His6 (SEO ID NO: 22) antibody so it is presumed that the 25kDa species contains uncleaved signal peptide. Molecular weight standards are indicated on the left in kDa.

FIG. 6 is a graphic representation of the effect of PDGF-C (VEGF-X) or the PDGF-C CUB domain of human coronary artery smooth muscle cell proliferation. Cells were treated with E. coli-derived CUB or full-length PDGF-C proteins at the concentrations indicated.

MATERIALS AND METHODS

cDNA and Partial Genomic Cloning of VEGF-X

A profile was developed (Lee et al., 1996) based on the PDGF-like domain in known VEGF sequences (VEGF-A, B, C and D), and used to search the LifeSeq™ human EST database (Incyte Genomics Inc. Palo Alto, Calif., USA), The search revealed a partial sequence of a potential novel member of the VEGF family. To extend the cDNA sequence, 5′RACE was carried out using Marathon-Readyä placenta and skeletal muscle cDNAs (Clontech, Palo Alto, Calif., USA. The full coding sequence was then amplified using standard polymerase chain reaction methods (Fitz et al., 1997). PCR fragments were cloned into vectors pCR2.1 (Invitrogen, Carlsbad, Calif. USA) or pCR2.1-TOPO (Invitrogen, Carlsbad, Calif. USA). To determine the coding sequence, multiple clones were sequenced; also all subclones were verified by DNA sequencing. To obtain a partial genomic clone, a human genomic BAC library (Genome Systems, Inc., St Louis, Mich., USA) was screened by hybridization to oligonucleotides derived from the PDGF-C cDNA sequence. For determination of intron/exon boundaries, BAC DNA was sequenced directly using 20-mer sequencing primers based on the known cDNA sequence. BAC DNA was prepared using a Qiagen plasmid midi kit (Qiagen GmbH, Düsseldorf, Germany).

Chromosomal Localization of the VEGF-X Gene

Chromosomal mapping studies were carried out by See DNA Biotech Inc. (Toronto, Canada) using FISH analysis with a biotinylated 2.7 kb probe as described previously (Yamada et al., 1997; Gribsteor et al., 1987, Ausabel et al., 1997).

Analysis of VEGF-X mRNA Expression by Northern Blot and RT-PCR

Northern blots containing 2 μg of poly(A)+rich RNA derived from different human tissues (Clontech Laboratories; MTN™(Multiple Tissue Northern) blot, MTN™ (Multiple Tissue Northern) blot II and Cancer Cell Line MTN™ (Multiple Tissue Northern) blot) were hybridized with a a-[³²P]-dCTP random-priming labeled (Multiprime labeling kit, Roche Diagnostics) 293 bp specific PDGF-C fragment (PinAI-StuI fragment including 92 bp of the 3=end coding region and 201 bp of the 3=untranslated region of PDGF-C). The blots were hybridized overnight at 68°C. and final washes at high stringency were at 68°C. in 0.1×SSC/0.1% SDS. The membranes were autoradiographed for 1 to 3 days with intensifying screens. For RT-PCR analyses, oligonucleotide primers GTTTGATGAAAGATTTGGGCTTG (SEQ ID NO: 3) and CTGGTTCAAGATATCGAATAAGGTCTTCC (SEQ ID NO: 4) were used for the specific PCR amplification of a 350 bp fragment from PDGF-C. PCR amplifications were performed on human TM multiple tissue cDNA (MTC™) panels (Clontech human MTC panels I and II and human Tumor MTC panel) normalized to the mRNA expression levels of six different housekeeping genes. In addition, cDNA was made from different tumor cell cultures (Caco-2 colorectal adenocarcinoma; T-84 colorectal carcinoma; MCF-7 breast adenocarcinoma; T-47D breast ductal gland carcinoma; HT1080bone fibrosarcoma; SaOS-2 osteosarcoma; SK-N-MC neuroblastoma; HepG2 hepatoblastoma; JURKAT T-cell leukemia and THP-1 myelomonocytic leukemia). For the preparation of tumor cell cDNA, cells were homogenized and total RNA prepared using the RNeasy Mini kit (Qiagen GmbH, Hilden, Germany). 1μg of total RNA was reverse transcribed using oligo(dT)₁₅ as a primer and 50 U of EXPAND™ (a High Fidelity enzyme blend, which consist of Taq DNA polymerase and Pwo DNA polymerase, for DNA amplification).

Reverse Transcriptase (Roche Diagnostics, Mannheim, Germany). PCR reactions with PDGF-C-specific or glyceraldehyde-3-phosphate dehydrogenase (G3PDH)-specific primers were then performed on 1 μl of this cDNA. For all cDNAs, PCR reactions with PDGF-C specific primers were performed in a total volume of 50 μl. Samples were heated to 95° C. for 30 s and cycling was performed for 30 s at 95° C. and 30 s at 68° C. for 25, 30 or 35 cycles. Control reactions using specific primers that amplify a 1 kb fragment of the housekeeping gene G3PDH were also carried out.

Expression, Purification and Detection of Recombinant Proteins

For mammalian cell expression, the full coding sequence was amplified and cloned into the vector pcDNA6/V5-His (Invitrogen, Leek, Netherlands) to add a C-terminal His₆ (SEQ ID NO:22) peptide tag to assist in detection and purification. For E.coli expression, the coding region of the predicted mature protein (Glu23-Gly345) was PCR amplified to add a C-terminal His₆ (SEQ ID NO: 22) tag and then cloned into the vector pMAL-p2 (New England Biolabs, Beverly, Mass., USA). The resulting MBP fusion protein was purified first on Nickel chelate resin (Ni—NTA, Qiagen GmbH, Düsseldorf, Germany) and then on amylose resin (New England Biolabs, Beverly, Mass.). The DNA sequence encoding the CUB domain fragment of PDGF-C (Glu23-Val1 71) was PCR amplified to add an N-terminal His₆ (SEQ ID NO: 22) tag and cloned into pET22b (Novagen, Madison, Wis.) for secretion in E.coli. The CUB domain protein was prepared either from the periplasm or cell-free medium of induced cultures by standard methods (Fitz et al., 1997). The protein was initially purified by precipitation with 20% saturated ammonium sulphate. After overnight dialysis against 20 mM Tris pH 8.0, 300 mM NaCl to remove ammonium sulphate, the protein was further purified on Nickel chelate resin as described above. Analysis of protein glycosylation was carried out using N-glycosidase F (Roche Molecular Biochemicals, Brussels, Belgium). Heparin Sepharose columns (HiTrap , Amersham Pharmacia Biotech, Uppsala, Sweden) were used according to the manufacturer=s instructions. Before use in cell-based assays, protein samples were tested for endotoxin contamination using a commercially available kit (COATEST7 Endotoxin, Chromogenix AB, Sweden).

Cell Culture

Human umbilical vein endothelial cells (HUVECs) (Clonetics, San Diego, Calif.) were maintained in EGM-2 growth medium (Clonetics, San Diego, Calif.) and human skeletal muscle cell (SkMC) (Clonetics, San Diego, Calif.) were cultured in skeletal muscle growth medium (Clonetics, San Diego, Calif.). The cells, including HCASMs (Clonetics, San Diego, Calif.), rat heart myocardium H9c2 (American Type Cell Collection, Rockville, Md.), and human neonatal dermal fibroblasts (39-SK) (American Type Cell Collection, Rockville, Md.), were maintained in Dulbecco's modified Eagle medium (DMEM) (Gibco, Gaithersburg, Md.) supplemented with 10% fetal bovine serum (FBS) (HyClone, Logan, Utah), 6 mM Hepes, 50 I.U./ml of penicillin and 50 μg/ml of streptomycin. The cells were used between passage 4-6. Human osteoblasts (MG 63) (American Type Cell Collection, Rockville, Md.) were maintained in DMEM supplemented with 10% FBS, 100 U/ml penicillin and 100 μg /ml streptomycin. Primary chondrocytes were isolated from bovine shoulders as described previously (Masure et al., 1998). Primary bovine chondrocytes were cultured in DMEM (high glucose) supplemented with 10% FBS, 10 mM HEPES, 0.1 mM non-essential amino acids, 20 μg/ml L-proline, 50 μg/ml ascorbic acid, 100 μg/ml penicillin, 100 μg/ml streptomycin and 0.25 μg /ml amphotericin B (chondrocyte growth media). All cell cultivation was carried out at 37° C. in a humidified incubator in an atmosphere of 5% CO₂ and 95% air.

Cell Proliferation Assay

HUVECs were trypsinized with 0.05% trypsin/0.53 mM EDTA (Gibco, Gaithersburg, Md.) and distributed in a 96-well tissue culture plate at 5,000 cells/well. Following cell attachment and monolayer formation (16 hours), cells were stimulated with various concentrations of VEGF-X in DMEM containing 0.5% to 2% FBS as indicated. For human dermal fibroblasts, the growth medium was replaced by DMEM containing 0.1% BSA with or without various concentrations of VEGF-X. For MG63, human SkMC, H9c2 or HCASMC, the medium was replaced by DMEM containing 0.5% FBS. Bovine chondrocytes were seeded in a 96-well tissue culture plate at 5,000 cells/well in a high glucose DMEM medium supplemented with 10% FBS and allowed to attach for 72 h. Medium was replaced by DMEM containing 2% BSA with or without treatments for two days. For all the cells tested, after incubation with the treatments, the culture media were replaced with 100 ml of DMEM containing 5% FBS and 3 μCi/ml of [³H]-thymidine. Following pulse labeling, cells were fixed with methanol/acetic acid (3:1, vol/vol) for 1 h at room temperature. The cells were washed twice with 250 ml/well of 80% methanol. The cells were solubilized in 0.05% trypsin (100 ml/well) for 30 min then in 0.5% SDS (100 ml/well) for another 30 min. Aliquots of cell lysates (180 ml) were combined with 2 ml of scintillation cocktail and the radioactivity of cell lysates was measured using a liquid scintillation counter (Wallac 1409).

Chromosomal Localization and Intron/Exon Structure of the PDGF-C Gene

VEGF-X was localized on the long arm of human chromosome 4, region q31-q32 by FISH analysis (FIG. 2). The hybridization efficiency was ˜70% for this probe. Database searches identified two genomic BAC clones which carry VEGF-X sequences (EMBL accession numbers AC009582 and AC015837). These BAC clones were derived from chromosome 4, supporting the FISH data. A BAC clone was isolated which contained the 3′ part of the cDNA. By direct sequencing this clone the positions of a splicing event in the PDGF domain region of the cDNA could be deduced (nt. position 1179/1180 in FIG. 1). The position of this splice site is conserved with respect to VEGF-A and VEGF-D (Heng et al., 1993, Hagen et al., 1994). The positions of the other splice sites shown in FIG. 1 were deduced from the sequences of database BAC clones AC009582 and AC015837 described above.

Summary of Testing VEGF-X and CUB Domain

Neither the VEGF-X or CUB domain increased the proliferation of human dermal fibroblasts, human umbilical endothelial cells, bovine chondrocyte or human osteoblast cells (MG 63). However, both full-length and CUB domain constructs were able to stimulate proliferation of human coronary artery smooth muscle cells in a dose-dependent manner (FIG. 3). The optimal stimulatory concentration was in the range from 1-10 μg/ml. The effect of both the full-length or CUB domain construct, at the highest concentration tested, was four-fold over the control level (FIG. 2). We did not observe this mitogenic activity of the CUB domain on other muscle cell types, such as human skeletal muscle cells or rat heart myocardium (data not shown). Following deletion of the third cysteine or mutation to a serine residue, we found the mitogenic activity of the CUB domain on the human coronary artery smooth muscle cells was reduced to about half at the highest concentration (10 μg/ml) (data not shown).

TABLE 1 Comparison of pairwise identity and similarity for PDGF-C and related proteins % IDENTITY % SIMILARITY CUB NRP_XENLA 35 50 NRP_MOUSE 33 46 NRP_CHICK 32 48 BMP1_XENLA 28 44 BMP1_HUMAN 24 41 PDGF VEGFB 29 47 VEGFD 29 44 PDGFB 29 40 PDGFA 29 39 VEGFA 25 51 VEGFC 24 43 PLGF 23 42 VEGF-A vs VEGF-C 38 51

Comparisons are between the regions of the proteins shown in FIG. 2, calculated with the Genedoc program (http://www.cris.com/˜Ketchup/genedoc.shtml)

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1. A method of stimulating smooth muscle cell proliferation in tissues or organs and tissue repair in a subject comprising administering to said subject an amount of a CUB domain of VEGF-X polypeptide consisting essentially of the sequence from position 40 to 150 of the amino acid sequence depicted in SEQ ID NO: 7 or a polypeptide encompassing conservative amino acid changes thereof, in sufficient concentration to stimulate smooth muscle cell proliferation, wherein conservative amino acid changes include replacement of one or more amino acids of SEQ ID NO: 7 which do not affect the function of SEQ ID NO:7; and wherein the conservative amino acid changes result in a polypeptide having at least 95% amino acid homology to the amino acid sequence depicted in SEQ ID NO:7.
 2. A method of treating smooth muscle cell hypoproliferation comprising applying a therapeutically effective amount of any of a CUB domain consisting essentially of a polypeptide from position 40 to 150 of the amino acid sequence depicted in SEQ ID NO: 7 or a polypeptide encompassing conservative amino acid changes thereof, and a pharmaceutically acceptable carrier, diluent or excipient thereof, wherein conservative amino acid changes include replacement of one or more amino acids of SEQ ID NO:7 which do not affect the function of SEQ ID NO:7; and wherein the conservative amino acid changes result in a polypeptide having at least 95% amino acid homology to the amino acid sequence depicted in SEQ ID NO:7. 